Sportscience · sportsci org News & Comment / Training & Performance

Acute Effects

"Even minor changes in natural (day-to-day) variation in sleep quantity significantly affected cognitive and gross motor performance" over three consecutive days in 98 elite youth athletes. [KNUFINKE, M]. But the results were presented only as p=0.03 and p=0.04, and with repeated measurement in such a large sample, these significant effects would likely be definitively trivial. As always, we need to see an assessment of the magnitude of the confidence limits. (See the item and slideshow on p values in this issue, if you don't understand how a significant effect can be trivial.)

I can't be sure, but it looks like an unspecified amount of one night of sleep deprivation in trained cyclists impaired ~1-h time-trial time by 11% ("p<0.05"). [ROBERTS, S.S.H]

"Poor sleep was associated with worse age-group rank" (r=0.37) in this study of 30 Ironman triathletes. [PAHNKE, M]

They was only an unstated number of participants, and effects are presented only in standardized units (please don't!), but it looks like extra sleep enhances sprint performance. [PITCHFORD, N.W]

"Urine metabolomics" (analysis of the pattern of metabolites in urine) showed changes when sleep was disturbed with exposure to bright artificial light in eight healthy men. [NAKAMURA, Y]. I wonder if such analysis could be useful in monitoring acute and chronic fatigue.

An unspecified number and type of athletes "experienced poor sleep following a night game. Further, athletes with a high trait arousal [reported more] sleep complaints". [JULIFF, L.E]

Exposure of male athletes to bright light for 60 min appears to enhance evening performance of a 12-min cycling time trial, but I missed the presentation and it's not clear what "tenfold increase in exposure to non-image forming light" in the abstract refers to. The "performance gain… of 6.2%" presumably refers to work, not time. [KNAIER, R]

What kind of morning exercise (at 0830) might enhance performance in the afternoon (at 1300)? In this crossover study of 12 cyclists, 6x 6-s sprints enhanced 5-km time trial time by a presumably unclear 0.6% compared with control (no exercise), but "ecological exercise" (some anaerobic threshold bouts plus 2x sprints) produced a possible enhancement of 1.6%. [DONGHI, F]

As a result of this crossover study of 20 male judokas, the authors suggested performing a "combine" warm-up (presumably static and dynamic) before training skills based on speed and strength performance, and a static warm-up before skills to improve flexibility performance. [EKEN, Ö]

Two bouts of active muscle stretching are enough to achieve a more than two-fold greater increase in range of motion than static stretching with the same time under loading in this crossover with 18 recreationally active subjects. [KAY, A.D]

A post-activation potentiation protocol specific for swimming (three sets of maximal isometric contractions in the start position) "significantly" improved 15-m start time of 12 national-level freestyle swimmers by 0.07 s. [VIEIRA, L]. This represents a ~0.3% improvement in 50-m time, for which the smallest important change is similar (~0.25%).

It was mainly a mechanisms study of 32 subjects, but the results "highlight the potential for [10 maximal] hops as a conditioning activity to potentiate subsequent performance" of drop jumps and actions involving the stretch-shortening cycle. [KÜMMEL, J]

Back-squat exercise with elastic bands produced a greater potentiating effect on vertical jumps than with free weights in 15 active men, although it appears to be a difference in significance rather than a significant difference. [MINA, M.A]

One or two half squats were probably better than three for potentiating acceleration in repeated sprints in this study of 20 athletes. [GOEBEL, R]

In a crossover simulation of game activity run on a treadmill in the heat, eight semi-professional soccer players experienced an increase in core temperature of 2.3°C in the control condition, but increases of 1.9 and 2.0°C respectively when they drank cool water and placed an ice towel around the neck during 3-min breaks at 30 min into each half. An extra 5-min break at half time produced an increase of 2.1°C. The changes relative to control were described as likely large through likely small. Magnitude thresholds were not described and the cooling treatments were not compared inferentially, but even so, drinking cool water is likely to be most effective. [CHALMERS, S]

Use cooling strategies before and/or during an endurance run in the heat (33 °C)? Eleven trained male runners performed 20 min of pre-load running at 70% VO2max followed by a 3-km time trial (lasting ~14 min) in each of four conditions in crossover fashion: pre-cooling by cold-water immersion and ice-slurry ingestion, mid-cooling by facial water spray and menthol mouth rinse, pre- and mid-cooling combined, and control. Compared with control, the athletes ran faster by 2.1% with pre-cooling and by 3.5% with mid-cooling and the combined methods. Enhancements in a longer time trial without the pre-load would be about half these values, and the smallest important enhancement for runners is ~0.3%, so the authors' conclusion that pre-cooling "had little or no influence" is obviously wrong. Allowing for sampling variation, I recommend pre- and mid-cooling. [STEVENS, C]

Iced towels and a fan plus moisture applied to the skin were equally effective at reducing rectal temperature of tennis players during mandated breaks in play in the hot conditions of the Australian and US Opens. [LYNCH, G]

"Coaches should emphasize stance width in their instruction for football goal keepers, because the small difference [in dive time between a width of 75% of leg length vs 50%, 100% or self-selected width] reflects a travel distance of the ball of 1.2 m in a penalty situation, and a 20 cm longer reach of the goal keeper at ball contact." It was a crossover with 10 elite goalies. [IBRAHIM, R]. I would have given this study a Wow!, if the authors had properly addressed uncertainty in the magnitude of the effect.

A "novel dynamic tape" applied to the gastroc improved jump performance (p values only) in 18 participants with chronic ankle instability. [KODESH, E]

There was a session of six presentations on pacing in cycling and winter sports, which I did not attend. [OP-PM31]. The presentation with the most practical application: "Performance at the start [of ski cross and snowboard cross] is crucial for succeeding in the race. Therefore relevant movement parameters for a good start have to be investigated and then trained systematically." [SPITZENPFEIL, P]. Biomechanical analysis of the start in this study is reported in a separate abstract, with results "suitable for recommendation for coaches and athletes". [OLVERMANN, M]

Sixteen U-19 elite soccer players showed no decline in performance when they immediately repeated the Loughborough soccer-specific repeated sprint ability test, even though their perceived fatigue was way higher. [O'REILLY, J]. Maybe cognitive skills suffered, as shown by the next abstract.

"Mental and physical fatigue impaired reactive agility and basketball skill performance" in 11 male, recreational basketball players. [SMITH, M]. Sure, but the mental fatigue was the Stroop test, which no coach in her right mind would get athletes to do before a match.

A computer-based cognitive task performed between small-sided games induced extra mental fatigue in 40 young soccer players that might increase resistance to mental fatigue in games, if included in the training program. [BOSIO, A]

I missed the symposium on individualization in recovery. The first presenter highlighted the need for "individualizing cut-off values for single markers and/or joint consideration of several parameters". Unfortunately the abstract is of the results-will-be-presented variety, but see below for my summary of her co-worker's application of the method. [HECKSTEDEN, A]. The second presenter's abstract is also minimally informative, but see my summary of her presentation in the satellite symposium above. [HALSON, S]. The only practical advice in the abstract of the third presenter was "grouping together players exhibiting similar chronotype in shared rooms to prevent sleep disturbance during training camps and/or away competitions". [NEDELEC, M]

A single exposure to sauna post-exercise impaired performance of 20 well-trained swimmers and triathletes in the following swim-training session. "Athletes should abstain from sauna bathing prior to competition and hard training sessions", although carefully planned long-term use may be beneficial. [SCHIMPCHEN, J]

"Whole-body compression garments and neuromuscular electrical stimulation do not promote recovery [of blood biomarkers, perceived wellness and countermovement jump] after a cross-country elite sprint skiing competition." [GOVUS, A]

When a reputable researcher gives a symposium presentation on foam rolling, you have to take it more seriously. Reduction in pain and increase in range of motion are the main claims made for benefit. [BEHM, D]

A crossover study with 18 semi-professional football players showed that eccentric-based injury-prevention exercises should be scheduled 1 d rather than 3 d after a game, to reduce exercise-induced muscle damage and soreness before the next game. [LOVELL, R]